pokorny



Feb. 14, 1956 s. s. POKORNY POST HOLE DRILLER 2 Sheets-Sheet 1 Filed Aug. 11, 1952 Jnventm 1v Stephen $.Po5orn 33 r 4 l'lorngys "Wi m e55 Maw Feb. 14, 1956 s. s POKORNY 2,734,722

POST HOLE DRILLER Filed Aug. 11, 1952 2 Sheets-Sheet 2 R65 Er? van I CYLINDERS flnvenl ov Stephen 5. 4 01101213 W1 M56 23 M 4% {aw/QM; mromgys 2,754,722 POST HOLE DRILLER Stephen s. rokom Maquoketa, Iowa Application August 11, 19-52, Serial No. 303,739 13 Claims. (C1. "255 19 My invention is a hydraulic driven post hole driller which has a novel hydraulic circuit which prevents seri- 'ous damage to the unit as a result of the auger striking unyielding objects such as stones and the like.

There are numerous powered post hole diggers or'drillers on the market. Most of these units are mounted on tractors or other vehicles. Generally the means for driving the auger and raising or lowering the auger mechanism are-controlled entirely independently of each other. ,Most of the post hole diggers with which I :am familiar are mechanically driven usually from the power take-off of a tractor or truck. The raising and lowering means is frequently a manually driven Windlass or one that can be connected info the power take-off system by means of a clutch or the like. Since the auger of these units is driven directly by mechanical linkage of some nature any' sudden stopping of the auger as a result of striking a large rock or other unyielding object is apt to cause damage to theiinit or extensive delay'in operations when the unit is provided with a shear apin or some other technique for avoiding damage. to "the mechanism generally. Furthermore, considerable skill is required in using the unit since the rate at which the auger is lowered into the ground is controlled by 'nieans that are completely ih'de'pen'deht'of the force driving the auger. Most of these structures also require several universal joints and telescoping connections to --acc"om'- m'odate the various attitudes that the auger "might take in respect to "the frame work supportih'g'it ahdflthe ve hicle on which it is mounted. Those units whih "are raised and lowered by means of a 'manualiycperatea Windlass also have the shortcoming of beingrathei' limited in the amount ofdrilling which can lie-done between periods of clearing the hole and anger of loe's'eearth already drilled. Most of the Windlass raised machines where the Windlass is poweredby a manual handerank are not provided with sufiicient lWefage-tdfziihit the average person to extend the auger into theearfthto its full depth and then withdraw the augeribearing' the loose earth with it. It is necessary with these units to drill a portion of a post hole, withdraw and clea'r'the auger and'then return to the drilling operation again. This cycle is repeated until the hole is dee desired. Also because most "of these units'aie driven from the power take-off of the tracto'nt h'ey are menn'tea at the rear of the vehicle; and-anentirely separate struetiire 'for supporting the auger is necessary. Even ahe'ugh United States Patent ice 2,734,722 Patented Feb. 14, 1956 .2 known to me are not entirely satisfactory for the purposes for which they are intended.

In view of the foregoing, therefore, it is the primary object of my invention to provide a post hole driller that vhas an auger height controlling mechanism interconnected with themechanism for drivingthe auger which automatically stops auger feed or even withdraws the auger when it strikes anunyielding object.

It is a further object of my invention to provide a post holedriller that requires no universal joints.

It is a further object of my invention to provide a post hole driller that can be mounted on the lifting arms of any hydraulically operated loader.

It is a further object of my invention to provide a post hole driller that is provided with adequate power for raising it to permit drilling to the maximum depth of the auger in a single operation.

A still further object of my invention is to provide a post hole driller that is economical to manufacture and maintain.

These and "other objects will be apparent to those skilled in the art.

My invention consists insthe-construetion, arrangement, and combination of the various parts of the device, whereby the objects contemplated are attained as hereinafter more fully set forth, and specifically pointed out in my'claims, and illustrated in the accompanying drawings, in which;

Fig. 1 is a perspective viewof my post hole driller shown mounted on a tractor. some hidden parts.

Fig. 2 is a fragmentary plan view of my post hole driller with portions of the device broken away to illustrate its constructionin full.

Fig. an :a fragmentary yiewof my-posthole driller shown partly in longitudinal section. Broken lines illustrate an adjustmentof the mechanism'for height while dotted lines show an adjusted angular position of the auger.

Fig. 4 is a schematic diagram of 'the hydraulic system orcircuit toroperating rnvpost hole driller.

Referring to the draWings-Ihave used thenumeral -10 to designate an ordinary farmrtractor which is one "type of vehicle on which my post hole driller is mounted conveniently. Secured to the trac'tor is the elongated frame lifting armstructure designated v12 which is merely the lifting 'arm structure of a type frequ'ently used in hydraulic loaders. The ;particular structure of this lifting armincluding'theupright elements 14-on1y one of whichis visiblein Fig. 1 and th'e hydraulic cylinders 16 are obviously not-inventive except perhaps in "connection with the-balance of my structure. The elongated movable frame elenient -llmus't, of course, "be pivotally secured to the uprights 14 while the hydraulic cylinders are necessarily tpivotally secured both-to the uprights and to'the frame :12. Hydraulic fiuid underpre'ssure is applied totheey-linders "16 by'lany suita'hle conduit such as the; one'designated lflih Fi'g. 1.

At theouter end-offrameslflwwhichextends beyond the tractor longitudinally, Ithe a-u'g'e'r assembly is piveta-11y secured. auger assembly :co'nsists oi theauger 20.;and its supporting and driving mechanism.

The driving -mechanisin comprises a hydraulic-motor designated '22 whichhas a vr-pulley 124 secured to the motor shaft. A much larger V=type'pulley designated 264s secured-tattle auger shaft '28. A V-bel't 31) reeved around the pulleys s'erves tov-transmit-ipowerfrom one to the otherin the.-usualwmanner. The motor and the auger are. secured to the :channel element "or bearing su apmt beam 32 inany suitable umanner. The bearing block .34 extends the bearing'rsnrface lfor'fthe auger to give the Broken lines illustrate auger stability with reference to the bearing support 32. The center portion of the channel bearing support 32 is solid and adds its bearing surface to that of bearing block 34. This structure is most clearly understood by comparing the broken away fragment of the bearing support shown in Fig. 2 with the longitudinal sectional showing in Fig. 3 at 36 where the solid nature of the center portion of bearing support 32 is clearly disclosed. At the ends of the support element 32, the structure is a true channel however with end members as at 38 in Fig. 2 rigidly secured thereto in any suitable manner. A mounting bearing designated 40 is rigidly secured in the channel to provide mounting bolts 42 a broad bearing surface. This broad bearing surface permits the mounting bolt 42 to extend several inches beyond support element in 38 without causing the bolt to wobble. A pair of nuts designated 44 are used to determine the amount of mounting bolt 42 that extends beyond the support member 32 and provide a means for locking the bolt in the proper mounting position. This mounting bolt structure is important since it permits the use of a single size of supporting channel member 32 to be adjusted to numerous different loader frame structures.

The element 32 is constructed of a. size which permits it to be mounted on the smallest standard size of loader frame while the rigidly extendible bolts permit its adaptation to all of the larger commonly used sizes. This mounting bolt structure is used on both ends of element 32 and together provide an adjustment of several inches. As the elements on both ends are identical the same numerals have been used. Hydraulic conduits of a well-known type such as those designated 46 and 48 carry hydraulic fluid under pressure to the motor and provide a return line to the hydraulic reservoir. The auger is a well-known type with the possible exception of the cutting edge which is curved rather than straight as shown in Fig. 1 in numeral 50. This curved leading edge aids the auger in avoiding sudden stoppages as a result of encountering extremely hard earth or unyielding objects such as rocks and the like. As becomes apparent in the discussion of the hydraulic circuit any slight delay or retarding of the speed of the auger before a complete stoppage of the unit occurs will permit suificient time for the machine to react to protect itself against serious damage. At one side of the bearing support 32 an arm is extended a short distance above the bearing support 32. This arm may be formed from any suitable material and the one shown in Figs. 1, 2 and 3 and designated 52 is formed from a piece of angle iron. An elongated rod 54 that is pivotally secured to the arm 52 extends rearwardly to a control lever 56. The lower end of lever 56 is pivotally secured to some suitable tractor structure and the operator may raise the point of the auger by exerting a pull on lever 56. This action is clearly disclosed by the dotted lines shown in Fig. 3.

This description completes the major mechanical structure of my device as distinguished from the hydraulic circuits.

The hydraulic circuit as disclosed in Fig. 4 has the necessary and well-known elements of the usual hydraulic circuit and in addition some novel interrelated parts. A catalogue of obvious and well-known parts includes the reservoir 58, the pump 60, the normal pressure relief valve 62, a manually operated control valve 64, the hydraulic lifting cylinders '16, the cylinder bleeder valve 68, and the hydraulic motor 22. These units are connected by the usual type of hydraulic conduits which are designated by the following numerals: The conduit on the pump inlet 72, the conduit on the pump outlet to the relief valve inlet 74, the return line from the relief valve to the reservoir 76, the line from the relief valve to the control valve inlet 78. The pressure lines to the cylinders have already been designated by the numeral 18 (the numeral 18 is also used to designate the conduit from the control valve to the junction of the two separate lines leading to the lifting cylinders), the line leading from the lifting cylinder line 18 to the bleeder valve 68 is designated 80, the line from the bleeder valve to the reservoir 82, the line from the control valve to the motor 46 and the return line from the motor to the reservoir 48. The control valve 64 is a well known three port unit which has a mechanism inside of it permitting the line 78 from the relief valve to be connected to either the pressure line 46 to the motor or the pressure line 18 to the lifting cylinders or to completely block the flow of hydraulic fluid from the pump and relief valve.

In the bleeder or lifting cylinder return line 82 is imposed a plug type valve designated 84. The plug of the valve 84 has arm 86 connected to it rigidly. In the line extending to the motor from the control valve 64 is a pressure responsive unit 88 which changes hydraulic pressure into mechanical movement. The unit consists of a short element of conduit inserted in line 46 with a portion of one of its sides formed by a movable piston designated 90. A rod or other mechanical linkage 92 is connected to the piston and extends through the case of unit 88. The rod 92 is pivotally connected to the rod 86. A spring or other resilient means 94 constantly urges the piston 90 toward the hydraulic fluid flowing in line 46. A second relief valve designated 96 is also imposed in line 46. The return line from the second relief valve is connected to the cylinder pressure line 18. This completes the description of the operation and advantages of my post hole driller.

In order to drill a post hole with my machine the operator after first having raised the movable frame 12 to a position that causes the auger to clear the ground merely drives the vehicle on which the machine is mounted to the location at which the hole is to be drilled. The auger is raised, of course, by positioning the control valve 64 so that pump 60 can apply hydraulic fluid under pressure to the lifting cylinder pressure conduits 18. While the machine is being transported, bleeder valve 68 and control valve 64 are both positioned so as to prevent any flow of hydraulic fluid. Hydraulic fluid trapped in the lifting cylinders holds the auger in an elevated position. When the location at which it is intended to drill a hole is reached bleeder valve 68 is opened a suflicient amount to permit the gradual descent of the auger by permitting hydraulic fluid to escape from the cylinders into the reservoir by means of lines and 82.

If the post hole is a normal one that-is to be perpendicular, the operator merely permits gravity to hold the auger in a vertical position as it is lowered. If for any reason the post hole is to be drilled at an angle, the auger can be placed in almost any angular position by means of lever 56. When the guide point of the auger is properly positioned at the approximate center of a proposed post location, control valve 64 is positioned as shown in Fig. 4 so that hydraulic pump pressure is applied to the pump pressure line 46 of motor 22. As the motor rotates under the influence of hydraulic pressure, the pulleys 24 and 26 are rotated, the former by the pump and the latter by the V-belt which connects the two pulleys together. Bleeder valve 68 is then opened a sutficient amount to produce what the operator estimates will be a proper rate of feed or descent for the auger. As the auger rotates'and its weight applies pressure on the auger it will drill into the ground in a well known fashion causing earth to be removed from the hole. In the event, however, that the anger is feeding too rapidly or for any other reason, resistance to the auger is such that the motor is slowed, then a hydraulic pressure begins to build up in line 46, pressure is applied to the end of piston 90. Spring 94 is set to resist pressures below a predetermined value. In my working structure this value Was arbitrarily set at eight hundred (800) pounds per square inch, which will be abbreviated p. s. i. hereafter. Whenever the pressure in jfiae 46 exceed eight hundred awaits, pi-stun p rt' eentrdl raid d conduit connecting he fir t pert eamed in a direfft'itin'b'fthe rok 16 said thre p'cit control valve to said relief valve, at adjacent rod 92in Fi .'4. Tlfis'indvernentwillje*tr 'i'ea'st Jone hydraulieeylinder, a conduit connecting the mitted to the plug type valve 84 which will tend o -'sfecor'rd -of "t e pens for said control valve to said hyit, thereby further -restrictiiig "the how at fluid "in the 5 draulic cylin er, a hydraulic motor, aconduit connecting said hydraulic'fiidtor to the third port of said three port control wire, a conduit c'oiinje'cting said hydraulic 'm tor together the remaining fluid in cyl pp to s' reservoir, 'a hydraulic cylinder return conduit thereby preventing any fui'lhr El e eIlt llhe aug l iiiilfil FSfVOl v i i i i its normal operatin speed is resented. Ifthe'aug'r can "s d dentrd valve to If the ilo'w bf fluid in this return tine rs dte r to said "conduit that c'o ects hydraulic cylinder, a shut-151T not 'free itself and resume normal o erating "spee the v Ve in said hydraulic cylln de'r 'return line, a pressure seeon'd'r'elief 'valve 96 will open at'soiiie'pr'edetefniined fespbnsiye means that converts fluid pressure into thev'al'u'e and apply this excess pre'ss'uretolhe cylinder lifting cha rii'cal mete nt'tappedinto "said conduit connecting lines 18. "When pressure is applied to lines 18, the cyl- V sai'd three ddr control valve to said hydraulic motor, 'i'nde'rs '16 extend and raise the auger a'way tram the linkage connecting the mechanical movement portion of obstruction, whatever it may be. {As soon as the anger said pressure responsive means to said shut-01f valve, a is raised, however, away tram whatever obstacle "was re entmeans yieldinigly holding said pressure responsive reducing ifs speed, and, thereby, causing the mere-ag ng means iin'aposition rhdt'c'anses said shut-elf valve to be pressure; the sp'eedjof the auger will immediately in I fdpen "when'pres'sure's applied to said hydraulic motor are cre'ase'to normal R. P. As soon 'as'the'normal seared a etermined value, and a bleedervalve in said of the auger can be established the excess pressure in line hydra lic cylinder return conduit in series with said Shirt- 46 will be dissipated rapidly causing relief valve 9 6ft'o oif valve; "said three'pbrt control valve having means close and allowing piston '90 under the influence draping "therein fdr "se l ecti y connecting said first port'to said 94 to return to the normal position shown in 4. 's'econd'fportandfsald third port. 7 The cylinder bleeder line is'reopehed asa result of the g '2, A hydraulic circuit'cofmprising, a reservoir, a pump movement of piston 90 back to its normal position-and having an inlet n'd 'o'utl'et, a conduit communicating the cylinders immediately begin to collapse and flc we'r between thefmle'tofsaid pump'and Said reservoir, 3 three the auger again. Obviously my interconnected anger port relief valve, a conduitconnecting the outlet of said drive and height Control will automatically prevent "any 7 'p ii'm p 't e le said relief valve, a conduit connectmajor damage to the machine resulting from stoppage va ve to s'aidreservoir, a three port control of the auger. The curved leadingcuftin'g edge desig- 'vali ea conduit'con'necting the first .port of said three nated 50in Fig. l prevents any sudden complete stopport'con'trol'yaly'e to said relief valve, at least one hypage of the unit, and, therefore, permits the automatic 'd'r radar, a conduit connecting a second of the system'momentarily a period of increasing'pressure that lpoirts oifsa d "ohti'ol valve to said hydraulic cylinder, a

causes action to relieve the situation which is causing 35 ihydri1'iflic jm ei",""a conduit connecting said hydraulic the difiiculty. a meter inep port'qf said three port control valve, If the automatic "raising mechanism is constantly slowa second relief valve; said second relief valveinterposed ing or even raising the-auger lthe operatcr shouldeither reduce the feeding speed of the unit by 'closing =blgeder valve 68 somewhat or he should remove theau-ger from d connecting said third port of said three hydraulic motor, a conduit it Second rel ef valve to the conduit connectthe proposed post hole entirely and examine the hole 'Q g, id ll Q 5 h e P bo'fifrol Valve [0 ei to determine whether there is some obstacle =1'n 't heepath fiyd l b y liildei, afifdilfiuit connecting said hydraulic of the hole which would completelyprevent any possirnotd'r to'said ieservoi'r,--a hydraulic cylinder return cohbility of completing the hole at that exact location. 1f duit connecting sad reservoir to said conduit that con- -raise the auger away from the slag Which-prevents its 'device the only new portions being the unit 88,; relief "from the real spirit and purpose of my invention -a-nd "3 having an inlet and an outlet, aconduit-co'mniuh need "said "dontiol valve to said hydraulic cylinder, a N r "said hydraulic c'yl'inder return line, a rotation, the first relief valve 62 will prevent any serious [pi ss filejiespo nsl e means that converts fluid pressure damage by merely by-passing-pump measures back to in ch Inoyeitiefit tapped into said conduit conthe reservoir. From this description ;-o f operation it jil' t g, I d and of said three port control valve should be obvious that my novel hydraulic systernhas tofsaid'hydraulic n'io'ton'fl'inkage connecting the mechaninumerous advantages over many of-thepos-t hole drillers a flli i 3d Pr P mahs now on the market. Although it is a-relatively simple i for any reason it is impossible for the lifting cylinders-to valve 96 and the motor and auger assembly; -this-d riller canbe constructed for a price roughlyequ-iva-lent to the least expensive units now on the market and of which I have knowledge. On the other "hand this device-is a jd l j j u f S 'e l Said Shut- 5if v Said full-sized adequately powered post hole driller that will h fq p 3 Y having means therein, f r

perform in a manner equal to many of the'most ex- R 9 1y fifi'g {515m fif's'tvliloifll to Said setiond P pensive drilling machines known to -me. -It-is also-clear x id llfdjpo r't. by this time that my post hole driller will accomplish T Y m i C W g, a D P at-least my principalobject ofi-nvention. I 3 15111511 a t l cdmmuni'ca'tifig Some changes may be made-in the construction and i P iP d Q atfife arrangement of "my post 'hole driller without departing f i n d 'the ollflet of said I 'r ief valve, a conduit connectsaid reservoir, a three port conit dome-dang the first port 'of said three it is my intention to cover by my-cla ims, any-modified forms of structure or -use or" mechanical equivalents 5 which may be reasonably included within their's'cope. life to relief valve, at least many- I claim: fdi'aulicf'cyl nder acoiiduit connecting the second'of the l. A hydraulic circuit comprising, a reserVGi -aS ump s or deo'nt'i'ol valve to said hydraulic cylinder, a

' {dra 'c motlonfaconduit connecting said hydraulic a 'to"the-'third' ort' of 'said "three'port control valve, a cohduft 6 ng ulic motor 'to said "res between the inlet of said pum and said reservo three 'p'ort'relief valve, mandate g of said pump to the inlet of's'aidrellre valve, acondiiit ease; a hydraulic 'fcylinderfrfetui'n conduit connectin connecting said relief verve *to -saidr'sewoir, "t said' ie'sewdir tosa-id edildhitufat 'c'dnaeets "said control valve to said hydraulic cylinder, a shut-0E valve .in said hydraulic cylinder return line, a pressure responsive means that converts fiuid pressure into mechanical movement tapped into said conduit connecting said three port control valve to said hydraulic motor, means connecting the mechanical movement portion of said pressure responsive means to said shut-olf valve, a resilient means yieldingly holding said pressure responsive means in a position that causes said shut-off valve to be open when pressures applied to said hydraulic motor are below a predetermined value, and a bleeder valve in said hydraulic cylinder return conduit in series with said shut-off valve; said three port control valve having means therein for selectively connecting said first port to said second port and said third port.

4. A hydraulic circuit comprising, a reservoir, a pump having an inlet and an outlet, a conduit communicating between the inlet of said pump and said reservoir, a three port relief valve, a conduit connecting the outlet of said ptunp to the inlet of said relief valve, a conduit connecting said relief valve to said reservoir, a three port control valve, a conduit connecting the first port of said three port control valve to said relief valve, at least one hydraulic cylinder, a conduit connecting the second of the ports of said control valve to said hydraulic cylinder, a hydraulic motor, a conduit connecting said hydraulic motor to the third port of said three port control valve, a conduit connecting said hydraulic motor to said reservoir, a hydraulic cylinder return conduit connecting said reservoir to said conduit that connects said control valve to said hydraulic cylinder, a shut-off valve in said hydraulic cylinder return line, a pressure responsive means that converts fluid pressure into mechanical movement tapped into said conduit connecting said three port control valve to said hydraulic motor, linkage connecting the mechanical movement portion of said pressure responsive means to said shut-off valve, a resilient means yieldingly holding said pressure responsive means in one direction when pressures applied to said hydraulic motor are below a predetermined value, and a bleeder valve in said hydraulic cylinder return conduit in series with said shut-off valve; said three port control valve having means therein for selectively connecting said first port to said second port and said third port.

5. A hydraulic circuit comprising, a reservoir, a pump having an inlet and an outlet, a conduit communicating between the inlet of said pump and said reservoir, a three port relief valve, a conduit connecting the outlet of said pump to the inlet of said relief valve, a conduit connecting said relief valve to said reservoir, a three port con- 7 trol valve, a conduit connecting the first port of said three port control valve to said relief valve, at least one hydraulic cylinder, a conduit connecting a second of the ports of said control valve to said hydraulic cylinder, a

hydraulic motor, a conduit connecting said hydraulic motor to the third port of said three port control valve, a second relief valve; said second relief valve interposed in said conduit connecting said third port of said three port control valve to said hydraulic motor, a conduit connecting said second relief valve to the conduit connecting said second port of said three port control valve to said hydraulic cylinder, a conduit connecting said hydraulic motor to said reservoir, a hydraulic cylinder return conduit connecting said reservoir to said conduit that connects said control valve to said hydraulic cylinder, a shutoff valve in said hydraulic cylinder return line, a'pressure responsive means that converts fluid pressure into mechanical movement tapped into said conduit connecting the third port of said three port control valve to said hydraulic motor, linkage connecting the mechanical movement portion of said pressure responsive means to said shut-off valve, a resilient means yieldingly holding said pressure responsive means in one direction when pressures applied to said hydraulic motor are below a predetermined value, and a bleeder valve in said hydraulic cylinder return conduit in series with said valve; said three port control valve having means therein for selectively connecting said first port to said second port and said third port.

6. In a vehicle mounted post hole driller, an elongated frame adapted to be movably secured to a vehicle, hydraulic means secured to said frame and adapted to being secured to said vehicle to move said frame in relation to said vehicle, a bearing support member pivotally secured to said elongated frame, bearings secured to said bearing support, an auger journalled in said bearings, a V-pulley secured to said auger, a hydraulic motor secured to said bearing support member, a V-pulley secured to and driven by said motor, a V-belt reeved over said pulleys, a source of hydraulic pressure, a valve connected to said source of hydraulic pressure, pressure lines connecting said valve to said motor and said hydraulic means; said valve selectively connecting said source of hydraulic pressure to said motor and said hydraulic means, means for controllably releasing pressure from the one of said pressure lines connected to said hydraulic means, and a relief valve connected to both of said pressure lines for connecting the said pressure lines together when pressure in said motor reaches a predetermined value.

7. In a vehicle mounted post hole driller, an elongated frame adapted to being movably secured to a vehicle, hydraulic means secured to said frame and adapted to being secured to said vehicle to move said frame in relation to said vehicle, a bearing support member pivotally secured to said elongated frame, bearings secured to said bearing support, an anger journalled in said bearings, a V- pulley secured to said auger, a hydraulic motor secured to said bearing support member, a V-pulley secured to and driven by said motor a V-belt reeved over said pulleys, a source of hydraulic pressure, a valve connected to said source of hydraulic pressure, pressure lines connecting said valve to said motor and said hydraulic means; said valve selectively connecting said source of hydraulic pressure to said motor and said hydraulic means, means for controllably releasing pressure from the one of said pressure lines connected to said hydraulic means, a pressure responsive unit that transforms hydraulic pressure into mechanical movement connected to the one of said pressure lines that connects to said motor, a rod on said pressure responsive unit. which is activated when mechanical movement occurs, a valve in the one of said pressure lines that connects to said hydraulic means, an arm on said valve connected to the rod on said pressure responsive unit, and a relief valve connected to both of said pressure lines for connecting the said pressure lines together when pressure in said motor reaches a predetermined value.

8. In a mounted post hole driller, an elongated frame hingedly mounted on a vehicle, a hydraulic piston-operated cylinder hingedly secured to said elongated frame and the vehicle, an earth auger hingedly and rotatably secured to said elongated frame, a hydraulic motor mechanically connected to said earth auger, a source of hydraulic power, a control valve, a conduit connecting said control valve to said source of hydraulic power, a motor pressure line connecting said motor to said control valve, a cylinder pressure line connecting said cylinder to said control valve, a cylinder return conduit connecting said cylinder to said source of hydraulic power, a bleeder valve in said cylinder return conduit, a normally open valve in said cylinder return conduit, a cylinder vented to said motor pressure line, a spring loaded piston in said cylinder, and linkage connecting said piston to said normally open valve.

9. In a mounted post hole driller, an elongated frame hingedly mounted on a vehicle, a hydraulic piston-open ated cylinder hingedly secured to said elongated frame and the vehicle, an earth auger hingedly and rotatably secured to said elongated frame, a hydraulic motor mechanically connected to said earth auger, a source of hydraulic-power, a control valve, a conduit connecting said control valve to said source of hydraulic power, a motor pressure line connecting said motor to said control valve,

a cylinder pressure line connecting said cylinder to said control valve, a cylinder return conduit connecting said cylinder to said source of hydraulic power, a bleeder valve in said cylinder return conduit, a normally open valve in said cylinder return conduit, a cylinder vented to said motor pressure line, a spring loaded piston in said cylinder, a relief valve having a by-pass port mounted in said motor pressure line, a conduit connecting said by-pass port to said cylinder pressure line, and linkage connecting said piston to said normally open valve.

10. In a mounted post hole driller, an elongated frame hingedly mounted on a vehicle, a hydraulic piston-operated cylinder hingedly secured to said elongated frame and the vehicle, an earth auger hingedly and rotatably secured to said elongated frame, a hydraulic motor mechanically connected to said earth auger, a source of hydraulic power, a control valve, a conduit connecting said control valve to said source of hydraulic power, a motor pressure line connecting said motor to said control valve, a cylinder pressure line connecting said cylinder to said control valve, a cylinder return conduit connecting said cylinder to said source of hydraulic power, a bleeder valve in said cylinder return conduit, a relief valve having a by-pass port mounted in said motor pressure line, and a conduit connecting said by-pass port to said cylinder pressure line.

11. In a mechanism for driving and feeding a rotating cutting tool, a rotating cutting tool, a means connected to said tool for movably and rotatably supporting it, a

fluid pressure responsive means connected to said tool supporting means for moving said tool supporting means in one direction, a source of fluid pressure, means connected to said source of fluid pressure and said fluid pressure responsive means for conducting fluid under pressure from said source of fluid pressure to said fluid pressure responsive means, a means connected to said fluid pressure responsive means for trapping fluid under pressure in said fluid pressure responsive means; said trapping means also incorporating means for controllably releasing pressure from said fluid pressure responsive means, said source of fluid pressure connected to said rotating cutting tool, a spring-loaded piston means operatively associated with and actuated by said source of fluid pressure, said source of fluid pressure containing a control valve, an arm secured to said control valve, said spring loaded piston means actuating the arm of said control valve to increase fluid pressure applied to said fluid pressure responsive means when resistance to said rotating cutting tool exceeds a predetermined value.

12. In a mechanism for driving and feeding a rotating cutting tool, a rotating cutting tool, a means connected to said tool for movably and rotatably supporting it, a fluid pressure responsive means connected to said tool supporting means for moving said tool supporting means in one direction, a source of fluid pressure, means connected to said source of fluid pressure and said fluid pressure responsive means for conducting fluid under pressure from said source of fluid pressure to said fluid pressure responsive means, a means connected to said fluid pressure responsive means for trapping fluid under pressure in said fluid pressure responsive means; said trapping means also incorporating means for controllably releasing pressure from said fluid pressure responsive means, said source of fluid pressure connected to said rotating cutting tool, springloaded piston means connected in series with said trapping means and operatively associated with and actuated by said source of fluid pressure, said source of fluid pressure containing a control valve, an arm secured to said control valve, said spring loaded piston means actuating the arm of said control valve to render ineffective said means for controllably releasing trapped fluid from said fluid pressure responsive means at times, and a means operatively associated with and actuated by said source of rotating power that increases fluid pressure applied to said fluid pressure responsive means when resistance to said rotating cutting tool exceeds a predetermined value.

13. In a mechanism for driving and feeding a rotating cutting tool, a rotating cutting tool, a means connected to said tool for movably and rotatably supporting it, a fluid pressure responsive means connected to said tool supporting means for moving said tool supporting means in one direction, a source of fluid pressure, means connected to said source of fluid pressure and said fluid pressure responsive means for conducting fluid under pressure from said source of fluid pressure to said fluid pressure responsive means, a means connected to said fluid pressure responsive means for trapping fluid under pressure in said fluid pressure responsive means; said trapping means also incorporating means for controllably releasing pressure from said fluid pressure responsive means, said source of fluid pressure connected to said rotating cutting tool, a spring-loaded piston means operatively associated with and actuated by said source of fluid pressure, said source of fluid pressure containing a control valve, an arm secured to said control valve, said spring loaded piston means actuating the arm of said control valve to render inefi'ective said means for controllably releasing trapped fluid from said fluid pressure responsive means at times.

References Cited in the file of this patent UNITED STATES PATENTS 1,507,776 Humiston Sept. 9, 1924 2,123,897 Holmes July 19, 1938 2,410,508 Lamme Nov. 5, 1946 2,414,072 Taft Jan. 7, 1947 2,453,204 Dobbs Nov. 9, 1948 2,491,273 Lehner Dec. 13, 1949 2,516,182 Bury July 25, 1950 2,594,098 Vanderzee Apr. 22, 1952 2,624,551 Garner Jan. 6, 1953 

